Am 20.01.22 um 19:19 schrieb Heiko Carstens:
On Thu, Jan 20, 2022 at 01:56:40PM +0100, Heiko Carstens wrote:
2. Implementation changes
2.1 Modify common code
In general such changes are done in way that common code is or _may_ be
modified to fulfill our needs. Common code header file explicitely states
that architectures should get rid of private instances of
copy_{to,from}_user() and __copy_{to,from}_user{,_inatomic}().
So we should not add anything like that to arch code again, since nobody
would expect that.
Or to be more specific: I think the most simple solution would be to
try to get the new *key variants into include/linux/uaccess.h, and add
the raw variants in architecture code, similar to the rest of the
uaccess functions.
There is some (sort of) prior art with copy_mc_to_kernel() even,
though that can only partially be compared.
So in essence adding something like this and then providing raw_copy_from/to_user_key?
(whitespace damaged, just pasted in)
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index ac0394087f7d..3b6e78ee211c 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -201,6 +201,59 @@ copy_to_user(void __user *to, const void *from, unsigned long n)
return n;
}
+
+#if defined(__s390x__) && defined(CONFIG_KVM)
+/*
+ * Variants that pass along an access key. Uses by KVM on s390x to implement
+ * key checks for guests that use storage keys Must be kept in sync with the
+ * non-key variants from above. The only difference is the _key suffix when
+ * calling raw_copy_from/to_user_key.
+ */
+static inline __must_check unsigned long
+_copy_from_user_key(void *to, const void __user *from, unsigned long n, u8 key)
+{
+ unsigned long res = n;
+ might_fault();
+ if (!should_fail_usercopy() && likely(access_ok(from, n))) {
+ instrument_copy_from_user(to, from, n);
+ res = raw_copy_from_user_key(to, from, n, key);
+ }
+ if (unlikely(res))
+ memset(to + (n - res), 0, res);
+ return res;
+}
+
+static inline __must_check unsigned long
+_copy_to_user_key(void __user *to, const void *from, unsigned long n, u8 key)
+{
+ might_fault();
+ if (should_fail_usercopy())
+ return n;
+ if (access_ok(to, n)) {
+ instrument_copy_to_user(to, from, n);
+ n = raw_copy_to_user_key(to, from, n, key);
+ }
+ return n;
+}
+
+static __always_inline unsigned long __must_check
+copy_from_user_key(void *to, const void __user *from, unsigned long n, u8 key)
+{
+ if (likely(check_copy_size(to, n, false)))
+ n = _copy_from_user_key(to, from, n, key);
+ return n;
+}
+
+static __always_inline unsigned long __must_check
+copy_to_user_key(void __user *to, const void *from, unsigned long n, u8 key)
+{
+ if (likely(check_copy_size(from, n, true)))
+ n = _copy_to_user_key(to, from, n);
+ return n;
+}
+#endif
+
+
#ifndef copy_mc_to_kernel
/*
* Without arch opt-in this generic copy_mc_to_kernel() will not handle
